I'm pretty sure I once saw the Mishna Brura talk about how it's best not to cut tzitzis with metal and that there's a custom to cut tzitzis strings with your teeth. But now, although I keep searching through O.C. Siman 11, I can't seem to find it. Can anyone come up with marei mekomos?

would a ceramic blade knife be also an acceptable alternative to teeth and metal? Ceramic blades are made out of zirconium dioxide (ZrO2)
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user1111Dec 23 '11 at 17:59

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Isaac MosesDec 23 '11 at 18:10

@TzitzMan Yes, you can use a ceramic blade, and it is how most companies today cut their tzizit.
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aviDec 24 '11 at 16:24

@Ben ShmuelBrill gave you the Mare Makom in the Mishna Berura
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Hacham GabrielDec 25 '11 at 1:26